The present invention relates to a leakage tester, and particularly to a fuel cap leakage tester for testing whether a vehicle fuel cap seals properly against a tank filler neck of a vehicle and for testing whether interior valves of the fuel cap seal properly. More particularly, the present invention relates to a portable fuel cap leakage tester to which a fuel cap mounts during the leakage test after removal of the fuel cap from a tank filler neck of a vehicle.
It is desirable for fuel caps to seal properly the fuel tank filler necks of vehicles so that, for environmental reasons, fuel vapors are prevented from leaking into the atmosphere. Devices that test a fuel cap to determine whether the fuel cap seals properly against the filler neck of a vehicle and to determine whether the fuel cap has any other internal leaks are known. For example, Stant Manufacturing Inc. of Connersville, Indiana manufactures a Model No. 12440 fuel cap leakage tester that performs such a test. The Stant 12440 fuel cap leakage tester is designed for use at state vehicle inspection facilities and includes sophisticated electrical circuitry that operates during the test and that communicates test results automatically to a state computer that stores vehicle inspection data. See, for example, the disclosure in U.S. patent application No. 09/029,004, now U.S. Patent No. 5,996,402 to Robert S. Harris, which disclosure is incorporated by reference herein.
Monitoring of fuel cap integrity at locations away from state vehicle inspection facilities would be enhanced by provision of an inexpensive fuel cap leakage tester that is widely available at locations where fuel caps are sold, such as gas stations, automotive component parts stores, or large department stores having automotive departments. Consumers would welcome the widespread availability of a fuel cap tester that would alert them of the need to replace their fuel cap before their vehicle is examined during a state vehicle inspection. Store owners and gas station owners would also welcome such a fuel cap tester because they could quickly and inexpensively test customer's fuel caps to enable customers with failing fuel caps to detect leakage problems early and to purchase new fuel caps from the store owner or gas station owner as soon as the leakage problems are detected and before the caps are tested at a state vehicle inspection facility.
According to the present invention, a fuel cap leakage tester is provided comprising a fuel cap support, a pressure source, and a monitor. The fuel cap support is formed to include a test chamber and is adapted to receive a fuel cap to be tested in the test chamber to establish a pressurizable region therein and a sealed connection between the fuel cap to be tested and the fuel cap support. The monitor is positioned to communicate with the pressurizable region formed in the fuel cap support and is configured to measure air pressure in the pressurizable region. The fuel cap leakage tester further comprises means for communicating a flow of pressurized air from the pressure source to the pressurizable region with a predetermined pressure drop of the pressurized air therebetween. The predetermined pressure drop causes the pressure level of the pressurized air in the pressurizable region to be less than the pressure level of the pressurized air in the pressure source. The monitor measures the pressure level of the pressurized air in the pressurizable region during discharge of the pressurized air from the pressurizable region through an air leak path between the fuel cap to be tested and the fuel cap support at an unknown flow rate to determine whether the unknown flow rate associated with the fuel cap to be tested meets or exceeds a predetermined leakage flow rate. This measurement by the monitor establishes whether the sealed connection between the fuel cap to be tested and the fuel cap support complies with a predetermined fuel cap leakage rate specification.
In preferred embodiments, a fuel cap leakage tester is configured to receive and pressurize a fuel cap to be tested. The tester includes a pump with a handle that is "pumped" manually by an operator to charge a reservoir to which the pump is coupled. The reservoir includes a pressure-relief valve that operates to ensure that the reservoir is charged to a regulated pressure level. An outlet line from the reservoir is coupled though a series combination of an activation switch and a master orifice to a test base having an interior region into which a fuel cap to be tested is inserted. A pressure gauge is coupled to the test base to measure pressure within the interior region of the test base.
The activation switch is normally in a closed position so that, prior to the test, when the reservoir is being charged by the pump, no air flows from the reservoir to the test base. Either before or after the reservoir is charged, the fuel cap to be tested is inserted into the interior region of the test base to define a pressurizable region inside the test base. In certain cases, to facilitate attachment of a wide variety of fuel caps to a single test base, a customized cap adapter can be mounted in the interior region of the test base and a fuel cap can be mounted on the cap adapter customized to match the fuel cap to define a pressurizable region inside the test base and cap adapter.
During testing, the fuel cap is mounted on a fuel cap support defined by a test base or by a customized cap adapter mounted on a test base. The fuel cap support is formed to include a pressurizable region defined inside the test base or inside the test base and a cap adapter mounted on the test base.
To test the fuel cap after the reservoir has been charged, an operator moves the activation switch manually to an opened position which allows pressurized air to flow from the reservoir through the master orifice and into the pressurizable region in the fuel cap support in which the fuel cap to be tested is inserted. The rate at which the pressurized air flows from the reservoir through the master orifice is higher than the rate at which air leaks from the pressurizable region to the atmosphere. Leakage can take place between the fuel cap and the test base (or cap adapter) and/or through interior valving of the fuel cap. Thus, when the activation switch is moved to the opened position after the reservoir is charged, the pressure in the pressurizable region in the fuel cap support increases and the pressure gauge indicates this pressure increase.
If the difference between the flow rate of pressurized air through the master orifice and the leakage rate of air past the fuel cap is sufficiently large, the pressure in the pressurizable region in the fuel cap support will increase beyond a threshold level and the gauge will indicate that the fuel cap has passed the test. If the difference between the flow rate of air through the master orifice and the leakage rate of the air past the fuel cap is sufficiently small, the pressure in the fuel cap support will not increase to the threshold level and the gauge will indicate that the fuel cap has failed the test.
Additional features of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.